Low-fat diet may be low in benefitStudy of women shows no change in cancer, heart disease risks

11:55 PM CST on Tuesday, February 7, 2006By GINA KOLATA / The New York Times

The largest study ever to ask whether a low-fat diet reduces the risk of getting cancer or heart disease has found that the diet has no effect.

The $415 million federal study involved nearly 49,000 women ages 50 to 79 who were followed for eight years. In the end, those assigned to a low-fat diet had the same rates of breast cancer, colon cancer, heart attacks and strokes as those who ate whatever they pleased, researchers are reporting today.

"These studies are revolutionary," said Dr. Jules Hirsch, physician in chief emeritus at Rockefeller University in New York City.

"They should put a stop to this era of thinking that we have all the information we need to change the whole national diet and make everybody healthy," said Dr. Hirsch, who has spent a lifetime studying the effects of diets on weight and health.

The study, published in today's issue of the Journal of the American Medical Association, was not just an ordinary study, said Dr. Michael Thun, who directs epidemiological research for the American Cancer Society. It was so large and so expensive, he said, that it was "the Rolls-Royce of studies." As such, he said, it is likely to be the final word.

"We usually have only one shot at a very large-scale trial on a particular issue," he said.

The study was part of the Women's Health Initiative of the National Institutes of Health, the same program that showed that hormone therapy after menopause might have more risks than benefits.

The results, the study investigators agreed, do not justify recommending low-fat diets to the public to reduce their heart disease and cancer risk. The investigators added that the best dietary advice, for now, was to follow federal guidelines for healthy eating, with less saturated fats and trans fats, more grains, and more fruits and vegetables.

Not everyone was convinced. Some, like Dr. Dean Ornish, a longtime promoter of low-fat diets and president of the Preventive Medicine Research Institute in Sausalito, Calif., said that the women did not reduce their fat to low enough levels or eat enough fruits and vegetables, and that the study, even at eight years, did not give the diets enough time.

Others said that diet could still make a difference, at least with heart disease, if people were to eat the so-called Mediterranean diet, low in saturated fats like butter and high in oils like olive oil. The women in the study reduced all kinds of fat.

The diets studied "had an antique patina," said Dr. Peter Libby, a cardiologist and professor at Harvard Medical School. These days, he said, most people have moved on from the idea of controlling total fat to the idea that people should eat different kinds of fat.

But the Mediterranean diet has not been subjected to a study of this scope, researchers said.

And Dr. Barbara V. Howard, an epidemiologist at MedStar Research Institute, a nonprofit hospital group, and a principal investigator in the study, said people should realize that diet alone was not enough to stay healthy.

Except for not smoking, the evidence for advice on what makes a healthy lifestyle is largely indirect, Dr. Howard said.

Although all the study participants were women, the colon cancer and heart disease results should also apply to men, said Dr. Jacques Rossouw, the project officer for the Women's Health Initiative.

Dr. Rossouw said the observational studies that led to the hypothesis about colon cancer and dietary fat included men and women. With heart disease, he said, researchers have consistently found that women and men respond in the same way to dietary fat.

DIMINISHED BENEFIT

Researchers analyzed data from 48,835 women ages 50 to 79 between 1993 and 1998. About 40 percent were counseled to eat more fruits and vegetables and to cut their overall fat intake, with the goal of reducing their total fat consumption to no more than 20 percent of their daily calories.

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